I just read your post about Tamar. I have always wondered why God allowed that to happen.
Many people wonder why God allows bad things to happen... I believe that it's not so much that He allows bad things to happen, but that He allows all people the freedom to choose what they're going to do with their lives. His desire more than anything is for us to love Him, and second to love one another. But it must be a choice, otherwise we're all just robots that He controls. With the ability to choose to love Him (and others), we have the ability to reject Him (and others). It is through the human's rejection that others are so frequently hurt.
My parents chose to reject God... and me. As a child, I prayed earnestly that God would make my parents stop abusing me. But MAKING them stop would have been controlling. He is not a God who wants to control us. He wants us to love him so deeply that we choose to obey and respect Him. If my parents had made that decision, they never would have laid an evil hand on me.
It is true that not one person who lived in my home cared about my safety and well-being. In fact, no one in my extended family cared either. However, God placed many loving and trustworthy people in my life over the years. While my parents sinned against Him and against me, the Lord still provided for my needs. And, time and again, I see the amazing glory that He brings from the abuse I endured. I absolutely do not believe that it was God's will for me to be abused (or for Tamar to be raped), but I know that He can bring some serious beauty from ashes.
I believe with all my heart that God wanted for my parents to love Him and to love me. I believe the bottom line is that God does not force His will onto us (my parents, Tamar's brother, etc.). I believe that His will was absolutely to answer each of my prayers but He allows us free will in order that we will choose to love Him. Choosing to love him is what leads to truly loving one another.
"To all who mourn in Israel, he will give a crown of beauty for ashes, a joyous blessing instead of mourning, festive praise instead of despair. In their righteousness, they will be like great oaks that the Lord has planted for his own glory." Isaiah 61:3